Browsing > By author > Gkougkousi Katerina

Metamaterials have been of increasing interest in various applications fields, such as
absorbing shocks or vibrations, as well as damage prevention. So far, they have been
developed with a goal to increase toughness, reduce weight, increase durability of
structures, all of them aiming at fracture prevention. While conventional fracture
mechanics aims to prevent the initiation and propagation of cracks, a novel approach
seeks to utilize the phenomenon of fracture in our favour, by steering fracture through
exploiting the geometry of metamaterials. In this work, we aim to gain the opportunity to
precisely control and steer the crack propagation route in compression, by taking
advantage of controlling the metamaterials design and thus their mesh properties.
Starting from a deeper understanding of crack propagation during compression, we
investigate the mechanisms that determine the crack path in both brittle and ductile
materials. Firstly, we compress beams of different slenderness, cross section shape, and
materials, using a system of two displacement-controlled fixed grippers. We analyse with
both a high-speed and a regular camera, and we look into the simultaneous effect of
buckling and plasticity and its impact on the fracture propagation. For elasto-plastic
materials, if the plastic regime is already reached when the fracture starts, the effective
cross section area reduces during the crack propagation while the stiffness is
considerably reduced, causing an unusual fracture response. By tuning this effect,
designing more complex structures and applying our findings on fundamental beams to
them, fracture propagation can be used as a design tool, instead of being dreaded and
avoided. Our findings highlight the potential of intentionally directing fracture as a design
tool, opening up new avenues for the design of safer, more efficient materials in
applications where fracture control is critical, such as helmets and battery shells.